Solid-state reaction between strontium carbonate and silica

Abstract

Metastable SrSiO₃ was formed during the course of the reaction between an equimolar mixture of SrCO₃ and SiO₂. The reaction was found to proceed in four stages, (1)–(4). The overall reaction of (1) and (2) was best described 2 SrCO₃+ SiO₂→ Sr₂SiO₄+ 2 CO₂(1), SrCO₃+ SiO₂→ SrSiO₃(metastable)+ CO₂(2), SrSiO₃(metastable) [graphic omitted] SrSiO₃(stable)(3), Sr₂SiO₄+ SiO₂→ 2 SrSiO₃(stable)(4) by the Jander equation and the apparent activation energy was determined as 215.5 kJ mol^–1 irrespective of the ball-milling time. The increase in the reactivity caused by ball-milling was confirmed by thermal analysis (t.g.a. and d.t.a.). The effect of ball-milling is possibly interpreted in terms of the decrease in particle size of SrCO₃ in the early stages and of the improvement of SiO₂ dispersion in the later stages. The rate of formation of stable SrSiO₃ from Sr₂SiO₄ and SiO₂[reaction (4)] was determined. Reaction isotherms were best expressed by the Ginstling–Brounshtein equation and the activation energy was 510 kJ mol^–1.